2004 GMC Envoy Fuel Pump Fuse Location: A Complete Owner’s Guide
The fuel pump fuse on a 2004 GMC Envoy is located in the engine compartment fuse block, which sits on the driver’s side of the vehicle under the hood. For the 4.2L inline-six engine, the fuel pump is controlled by relay R2 (position 41), and the related fuse you should check first is the 20A “Powertrain Control Module B” fuse, listed as fuse #10 in the underhood fuse box. If that fuse is intact, the next components to inspect are the fuel pump relay itself, the PCM power feed, and the ground connection at G-107 on the engine block. This guide walks you through every step, from locating the fuse box to testing the relay, so you can get your Envoy cranking again without guessing.
Where to Find the Fuse Box on a 2004 GMC Envoy
The primary fuse block on the 2004 GMC Envoy is under the hood, on the driver’s side of the engine compartment. Open the hood and look toward the firewall on the left side; you will see a black plastic cover with a latch. Press the two locking tabs on top, then lift the primary cover. There is also a secondary cover underneath that snaps off when you lift it. Once both covers are removed, you will see the full layout of fuses and relays.
There is a second fuse panel located under the rear seat on the driver’s side, but the fuel pump fuse and relay are not in that rear block. The rear underseat fuse block handles body control functions, door modules, power seats, and similar accessories. So for any fuel pump issue, focus your attention on the engine compartment fuse block only.
Which Fuse Controls the Fuel Pump?
This is where many owners get confused. On the 2004 Envoy, there is no dedicated fuse labeled “Fuel Pump.” The fuel pump circuit is protected indirectly through a shared fuse. According to the factory fuse layout for the L6 4.2L engine, the fuel pump relay is labeled R2 (or position 41), and the fuse that feeds power to the PCM and the fuel pump circuit is the 20A fuse labeled “Powertrain Control Module B” (PCM B), which is fuse #10 in the underhood block.
Multiple owners on GM forums have confirmed this setup. One owner with a 2003 Suburban 5.3L shared a similar experience: the fuel pump died and blew the PCM B fuse, which also feeds the pump. The same configuration applies to the 2004 Envoy, where the PCM B fuse sits right next to the fuel pump relay, making it easy to check both at the same time.
For the V8 engine version, the layout is slightly different, but the same principle applies. The V8 underhood fuse block lists fuse #10 as “Powertrain Control Module B” as well, and the fuel pump relay remains at position 41. So regardless of whether your Envoy has the 4.2L inline-six or the 5.3L V8, start with fuse #10 and relay #41.
Step-by-Step: How to Check the Fuel Pump Fuse
Checking the fuse takes less than five minutes and requires only a test light or a multimeter. Here is the process:
1. Locate fuse #10 (PCM B). With the engine compartment fuse block cover removed, look at the diagram printed on the underside of the cover or refer to the fuse layout chart. Fuse #10 is a 20A mini fuse labeled “Powertrain Control Module B.” It should be in the same row as several other mini fuses.
2. Pull the fuse. Use the fuse puller that is stored inside the fuse block (it is clipped into the panel, often labeled as item #49). If you do not have the puller, a pair of needle-nose pliers works fine.
3. Inspect the metal strip. Hold the fuse up to the light. The metal element inside should be continuous from one prong to the other. If you see a break, a gap, or dark discoloration, the fuse is blown.
4. Test with a test light (optional). If the fuse looks fine visually but you want to be certain, touch one probe of your test light to each of the two small metal prongs on top of the fuse while it is still in the socket (with the ignition on). The test light should light up on both sides if the fuse is good. If it only lights on one side, the fuse is blown.
5. Replace if necessary. If fuse #10 is blown, replace it with a new 20A mini fuse. Do not use a higher amperage fuse, as that can damage the PCM or cause a fire. If the new fuse blows again immediately, you have a short in the fuel pump wiring or the pump itself.
The Fuel Pump Relay: Position 41
The fuel pump relay on the 2004 Envoy is a mini relay located at position 41 in the engine compartment fuse block. This relay is what actually delivers power to the fuel pump when you turn the ignition to the “ON” position. The PCM controls the relay by sending a ground signal to energize the coil.
If you have confirmed that fuse #10 is good, the next step is to test the relay:
1. Remove the relay. Grasp it firmly and pull straight out. It is a small black or dark-colored cube with four or five prongs on the bottom.
2. Check for battery power. With the ignition off, use a test light to check the relay socket. One of the large prong positions should have constant battery power. This is the supply side that comes from the fuse.
3. Turn the ignition to “ON.” You should now see power appear on another prong, which is the control side that the PCM switches. If you do not see power here, the issue may be with the ignition switch, the PCM, or a wiring problem.
4. Test the relay coil. Use a multimeter set to ohms to check the resistance between the two small prongs that connect to the coil. You should see a reading typically between 50 and 120 ohms. If you get infinite resistance, the relay coil is open and the relay needs to be replaced.
One forum member noted that on the 2004 Envoy with the 4.2L, they found battery supply on one side of the relay socket but no power on the PCM control side when the ignition was turned on. That points to either a bad PCM, a wiring fault, or a relay that is not being energized. If the relay tests fine and the fuse is good, the problem moves deeper into the circuit.
What to Do If the Fuse and Relay Are Both Good
If you have verified that fuse #10 is intact and the relay is working, but the fuel pump still does not prime, there are a few other things to check before condemning the pump itself.
1. Check the G-107 ground connection. This is a common and often overlooked cause. The fuel pump relay, the left headlamp, and the left turn signal all share a common ground point at the G-107 bolt-down location on the driver’s side of the engine block. If this ground connection is corroded or loose, it can cause enough resistance to prevent the fuel pump relay from operating. Look for a bolted eyelet connection with several black wires attached to the engine block. Remove the bolt, clean the contact surfaces with a wire brush, apply dielectric grease, and reinstall the bolt tightly.
2. Try jumping the relay. If you want to confirm whether the fuel pump itself is good, you can bypass the relay by using a fused jumper wire between the two large power terminals in the relay socket. With the ignition on, this should send power directly to the fuel pump. If the pump runs when you jump it, the pump is fine and the problem is in the control circuit. If it still does not run, the pump or the wiring to the pump is bad.
3. Inspect the underhood fuse block for internal damage. In some cases, the copper traces inside the fuse block itself can develop hairline cracks or corrosion between the upper and lower sections. This is a less common issue, but it has been documented on GMT360 platform vehicles like the Envoy and Trailblazer. If you have exhausted all other checks, the fuse block may need to be removed and inspected.
4. Listen for the pump. When you turn the key to “ON” (without cranking), you should hear a brief whirring sound from the rear of the vehicle for about two seconds. That is the fuel pump pressurizing the system. If you do not hear it, the pump is not receiving power, or the pump itself is dead.
Common Symptoms of a Fuel Pump Fuse or Relay Problem
Knowing the warning signs can help you catch this issue early or diagnose it faster when it happens:
1. Engine cranks but will not start. This is the most obvious symptom. The starter turns the engine over normally, but there is no fuel pressure, so the engine never fires. This is exactly what one owner experienced on the interstate when their 2004 Envoy 4.2L died while driving.
2. No fuel pump prime sound. When you turn the ignition to “ON,” you should hear the pump buzz for a second or two. If the fuse is blown or the relay is not engaging, you will hear nothing.
3. Headlights flickering. Because the fuel pump relay shares a ground with the left headlamp and left turn signal, a bad G-107 ground can also cause your left headlights to flicker or dim intermittently. One mechanic noted that owners may notice flickering headlights just before the engine dies.
4. Blowing fuses repeatedly. If you replace fuse #10 and it blows again after a short time, you have a short somewhere in the fuel pump power feed or the pump motor itself is drawing too much current. Do not keep replacing the fuse; find the root cause.
Tools You Will Need
Diagnosing a fuel pump fuse issue on a 2004 GMC Envoy does not require a professional mechanic’s toolset. Most of these checks can be done with basic hand tools:
1. Test light or multimeter. A simple 12-volt test light is sufficient for checking power at the fuse and relay. A multimeter is better if you also want to test the relay coil resistance.
2. Fuse puller. The Envoy comes with a fuse puller stored in the underhood fuse block, but needle-nose pliers work just as well.
3. Wire brush and dielectric grease. These are needed if you have to clean the G-107 ground connection.
4. Owner’s manual. The owner’s manual for the 2004 Envoy has a complete fuse diagram, and it is the most reliable reference for confirming the correct fuse and relay positions for your specific trim level.
Preventing Future Fuel Pump Fuse Issues
Once you have fixed the immediate problem, there are a few habits that can help you avoid repeating it:
1. Keep the fuse block clean and dry. Moisture and corrosion in the underhood fuse block can cause intermittent shorts and ground faults. Periodically inspect the fuse box for signs of water intrusion or green corrosion on the terminals.
2. Do not over-fuse. Always replace a blown fuse with the exact same amperage rating. Using a higher-rated fuse may allow the wiring to overheat and cause a fire.
3. Address weak grounds promptly. If you notice flickering headlights or intermittent electrical issues, check the ground connections early. A loose or corroded ground can cause a cascade of problems, including fuel pump relay failure.
4. Replace a failing fuel pump early. If the pump is making a loud whining noise, or if you experience occasional hard starts that gradually get worse, do not wait for the pump to fail completely. A failing pump will draw more current and can blow the PCM B fuse. Replacing the pump while it is still working is cheaper than being stranded.
Why the Right Fuel Pump Matters
If your diagnosis leads you to replace the fuel pump itself, it is critical to choose a high-quality replacement. The fuel pump is the heart of the fuel delivery system, and a cheap or poorly made pump can fail within months, leaving you with the same no-start problem all over again.
That is why we recommend considering KEMSO Fuel Pumps. KEMSO specializes in high-performance fuel pumps that are designed as direct OEM replacements and come with a lifetime warranty. Whether you drive a car, truck, motorcycle, ATV, or personal watercraft, KEMSO has a pump that fits your application and meets or exceeds factory specifications. With a lifetime warranty, you can be confident that your fuel pump will perform reliably for the life of your vehicle. Visit https://www.kemsoracing.com/ to browse their full lineup of fuel pumps and find the right one for your 2004 GMC Envoy or any other vehicle in your garage.
Final Thoughts
The 2004 GMC Envoy fuel pump fuse location is straightforward once you know where to look. The engine compartment fuse block on the driver’s side houses both the 20A PCM B fuse (number 10) and the fuel pump relay (number 41). Start by checking the fuse, then test the relay, then move on to the ground connection and the pump itself. Most no-start fuel pump issues on the Envoy trace back to one of these three components.
If you have gone through every step in this guide and the pump still does not run, the fuel pump motor itself is likely dead, and it is time to replace it. When that day comes, choose a pump that will not let you down. Check out KEMSO Fuel Pumps at https://www.kemsoracing.com/ for high-performance, OEM-replacement fuel pumps backed by a lifetime warranty. Your Envoy deserves nothing less.